#include <QPainter>
#include "graphitem.h"


static qreal yAtX(const QPainterPath &path, qreal x)
{
	int low = 0;
	int high = path.elementCount() - 1;
	int mid = 0;

	Q_ASSERT(high > low);
	Q_ASSERT(x >= path.elementAt(low).x && x <= path.elementAt(high).x);

	while (low <= high) {
		mid = low + ((high - low) / 2);
		const QPainterPath::Element &e = path.elementAt(mid);
		if (e.x > x)
			high = mid - 1;
		else if (e.x < x)
			low = mid + 1;
		else
			return e.y;
	}

	QLineF l;
	if (path.elementAt(mid).x < x)
		l = QLineF(path.elementAt(mid).x, path.elementAt(mid).y,
		  path.elementAt(mid+1).x, path.elementAt(mid+1).y);
	else
		l = QLineF(path.elementAt(mid-1).x, path.elementAt(mid-1).y,
		  path.elementAt(mid).x, path.elementAt(mid).y);

	return l.pointAt((x - l.p1().x()) / (l.p2().x() - l.p1().x())).y();
}

GraphItem::GraphItem(const Graph &graph, QGraphicsItem *parent)
  : QGraphicsObject(parent)
{
	_id = 0;
	_pen = QPen(QBrush(Qt::SolidPattern), 0);
	_type = Graph::Distance;

	_distancePath.moveTo(graph.distance.first(), -graph.y.first());
	for (int i = 1; i < graph.y.size(); i++)
		_distancePath.lineTo(graph.distance.at(i), -graph.y.at(i));

	if (!graph.time.isEmpty()) {
		_timePath.moveTo(graph.time.first(), -graph.y.first());
		for (int i = 1; i < graph.y.size(); i++)
			_timePath.lineTo(graph.time.at(i), -graph.y.at(i));
	}
}

void GraphItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
  QWidget *widget)
{
	Q_UNUSED(option);
	Q_UNUSED(widget);

	painter->setPen(_pen);
	painter->drawPath((_type == Graph::Distance) ? _distancePath : _timePath);
}

void GraphItem::setColor(const QColor &color)
{
	QBrush brush(color, Qt::SolidPattern);
	_pen.setBrush(brush);
}

qreal GraphItem::yAtX(qreal x)
{
	return ::yAtX((_type == Graph::Distance) ? _distancePath : _timePath, x);
}

qreal GraphItem::distanceAtTime(qreal time)
{
	int low = 0;
	int high = _timePath.elementCount() - 1;
	int mid = 0;

	Q_ASSERT(high > low);
	Q_ASSERT(time >= _timePath.elementAt(low).x
	  && time <= _timePath.elementAt(high).x);

	while (low <= high) {
		mid = low + ((high - low) / 2);
		const QPainterPath::Element &e = _timePath.elementAt(mid);
		if (e.x > time)
			high = mid - 1;
		else if (e.x < time)
			low = mid + 1;
		else
			return _distancePath.elementAt(mid).x;
	}

	if (_timePath.elementAt(mid).x < time)
		return ((_distancePath.elementAt(mid+1).x
		  + _distancePath.elementAt(mid).x) / 2.0);
	else
		return ((_distancePath.elementAt(mid).x
		  + _distancePath.elementAt(mid-1).x) / 2.0);
}

void GraphItem::emitSliderPositionChanged(qreal pos)
{
	if (_type == Graph::Time) {
		if (!_timePath.isEmpty()) {
			if (pos <= _timePath.elementAt(_timePath.elementCount() - 1).x)
				emit sliderPositionChanged(distanceAtTime(pos));
			else
				emit sliderPositionChanged(_distancePath.elementAt(
			      _distancePath.elementCount() - 1).x + 1);
		} else
			emit sliderPositionChanged(_distancePath.elementAt(
		      _distancePath.elementCount() - 1).x + 1);
	} else
		emit sliderPositionChanged(pos);
}